Actual source code: snesmfj.c

  1: #define PETSCSNES_DLL

 3:  #include private/snesimpl.h
 4:  #include ../src/mat/impls/mffd/mffdimpl.h
 5:  #include private/matimpl.h

  9: /*@C
 10:    MatMFFDComputeJacobian - Tells the matrix-free Jacobian object the new location at which
 11:        Jacobian matrix vector products will be computed at, i.e. J(x) * a. The x is obtained
 12:        from the SNES object (using SNESGetSolution()).

 14:    Collective on SNES

 16:    Input Parameters:
 17: +   snes - the nonlinear solver context
 18: .   x - the point at which the Jacobian vector products will be performed
 19: .   jac - the matrix-free Jacobian object
 20: .   B - either the same as jac or another matrix type (ignored)
 21: .   flag - not relevent for matrix-free form
 22: -   dummy - the user context (ignored)

 24:    Level: developer

 26:    Warning: 
 27:       If MatMFFDSetBase() is ever called on jac then this routine will NO longer get 
 28:     the x from the SNES object and MatMFFDSetBase() must from that point on be used to
 29:     change the base vector x.

 31:    Notes:
 32:      This can be passed into SNESSetJacobian() when using a completely matrix-free solver,
 33:      that is the B matrix is also the same matrix operator. This is used when you select
 34:      -snes_mf but rarely used directly by users. (All this routine does is call MatAssemblyBegin/End() on
 35:      the Mat jac.

 37: .seealso: MatMFFDGetH(), MatCreateSNESMF(), MatCreateMFFD(), MATMFFD,
 38:           MatMFFDSetHHistory(), MatMFFDSetFunctionError(), MatCreateMFFD(), SNESSetJacobian()

 40: @*/
 41: PetscErrorCode  MatMFFDComputeJacobian(SNES snes,Vec x,Mat *jac,Mat *B,MatStructure *flag,void *dummy)
 42: {
 45:   MatAssemblyBegin(*jac,MAT_FINAL_ASSEMBLY);
 46:   MatAssemblyEnd(*jac,MAT_FINAL_ASSEMBLY);
 47:   return(0);
 48: }

 50: PetscErrorCode MatAssemblyEnd_MFFD(Mat,MatAssemblyType);
 53: /*
 54:    MatAssemblyEnd_SNESMF - Calls MatAssemblyEnd_MFFD() and then sets the 
 55:     base from the SNES context

 57: */
 58: PetscErrorCode MatAssemblyEnd_SNESMF(Mat J,MatAssemblyType mt)
 59: {
 61:   MatMFFD        j = (MatMFFD)J->data;
 62:   SNES           snes = (SNES)j->funcctx;
 63:   Vec            u,f;

 66:   MatAssemblyEnd_MFFD(J,mt);

 68:   SNESGetSolution(snes,&u);
 69:   SNESGetFunction(snes,&f,PETSC_NULL,PETSC_NULL);
 70:   MatMFFDSetBase(J,u,f);
 71:   return(0);
 72: }

 76: /*
 77:     This routine resets the MatAssemblyEnd() for the MatMFFD created from MatCreateSNESMF() so that it NO longer
 78:   uses the solution in the SNES object to update the base. See the warning in MatCreateSNESMF().
 79: */
 82: PetscErrorCode  MatMFFDSetBase_SNESMF(Mat J,Vec U,Vec F)
 83: {

 87:   MatMFFDSetBase_MFFD(J,U,F);
 88:   J->ops->assemblyend = MatAssemblyEnd_MFFD;
 89:   return(0);
 90: }

 95: /*@
 96:    MatCreateSNESMF - Creates a matrix-free matrix context for use with
 97:    a SNES solver.  This matrix can be used as the Jacobian argument for
 98:    the routine SNESSetJacobian(). See MatCreateMFFD() for details on how
 99:    the finite difference computation is done.

101:    Collective on SNES and Vec

103:    Input Parameters:
104: .  snes - the SNES context

106:    Output Parameter:
107: .  J - the matrix-free matrix

109:    Level: advanced

111:    Warning: 
112:       If MatMFFDSetBase() is ever called on jac then this routine will NO longer get 
113:     the x from the SNES object and MatMFFDSetBase() must from that point on be used to
114:     change the base vector x.

116:    Notes: The difference between this routine and MatCreateMFFD() is that this matrix
117:      automatically gets the current base vector from the SNES object and not from an
118:      explicit call to MatMFFDSetBase().

120: .seealso: MatDestroy(), MatMFFDSetFunctionError(), MatMFFDDSSetUmin()
121:           MatMFFDSetHHistory(), MatMFFDResetHHistory(), MatCreateMFFD(),
122:           MatMFFDGetH(), MatMFFDRegisterDynamic), MatMFFDComputeJacobian()
123:  
124: @*/
125: PetscErrorCode  MatCreateSNESMF(SNES snes,Mat *J)
126: {
128:   PetscInt       n,N;

131:   if (!snes->vec_func) SETERRQ(PETSC_ERR_ARG_WRONGSTATE,"SNESSetFunction() must be called first");
132: 
133:   VecGetLocalSize(snes->vec_func,&n);
134:   VecGetSize(snes->vec_func,&N);
135:   MatCreateMFFD(((PetscObject)snes)->comm,n,n,N,N,J);
136:   MatMFFDSetFunction(*J,(PetscErrorCode (*)(void*,Vec,Vec))SNESComputeFunction,snes);
137:   (*J)->ops->assemblyend = MatAssemblyEnd_SNESMF;
138:   PetscObjectComposeFunctionDynamic((PetscObject)*J,"MatMFFDSetBase_C","MatMFFDSetBase_SNESMF",MatMFFDSetBase_SNESMF);
139:   return(0);
140: }